Category Archives: Retrochallenge

I have decided to enter Retrochallenge 2013. A spledid competition that runs throughout July every year.

Accoring to the website…

In a nutshell, the RetroChallenge is a loosely disorganised gathering of RetroComputing enthusiasts who collectively do stuff with old computers for a month.

And I have decided to use this as a dig in the ribs to try and get the Liberator going.

I’m not sure how I’ll do this blogging lark but I have a go while it’s fun 🙂

He Shoots… He misses…

So as Retrochallenge draws to a close for another year the Liberator is still not running.

One the plus side I have learned quite a bit about this interesting little machine. I have foubnd another one in the wild (well in Wales) and I have a certain admiration for its designers who gave the I/O board has its own processor to look after it. They gave it S5/8 ports instead of RS232. That should have been a great move. Sadly no one else followed.

It has memory cartridges, a bit like the USB memory sticks we take for granted and stacked RAM which usually looks like a dog’s breakfast but in this case uses eligant sockets.

This really is a nice machine. It just doesn’t work…

July 28 2013. Time is running out.

Things have not been going quite as swimmingly as I had hoped. Replcing the flexi cable between the two boards did not bring the beeps back as I had thought and so I’ve been sniffing around but really I’m just getting the lie of the land.

This is what I think… There are two main boards (I’m not counting the keyboard PCB. It’s not fair the passive components I know but that’s just the way I am). There is the lower board pictured above (ironically). It has a microcontroller with a piggybacked EPROM, two S5/8 ports, the keyboard connector the LCD and other bits and bobs. I’m calling this the I/O board.

The upper board has the CPU, the piggy back RAM and the main ROM. I’m calling this the CPU board.

The two boards are connected via the flexy PCB you’ve read about earlier.

The I/O board has the battery connector and so the CPU board is not a lot of use without its flexy umbilical. I’m not sure how far I should be able to get just playing with the I/O board. My guess is not very far as you don’t want the I/O board doing much more than initialising its peripheral controllers without the main CPU’s say-so.

This backs up what I’ve found. Without the CPU board the I/O doesn’t seems to do much. The problem is that it doesn’t do much with it either.

I do get a slight click from the piezo beeper when I connect a battery but that’s about it.

Hmmm. ‘scope time…

July 25 2013. Silent (not) running.

I mentioned in my last post that I’d had a problem with the flexi and made contac with another Liberator owner. Well it turns out that said Liberator owner, Peter, had an almost identical cable in his spares box and sent it over. Retro computing has some of the most generous people.

tonight I’ve carefully modded it to make it fit but I’m still not getting the old beep :-(. I seem to be getting 5V on the logic board but no signs of life.

time is running out but the saga continues.

July 21 2013. It’s all gone Pete Tong.

Things have not been going to plan just lately. It started very well. The new batteries were giving me a reassuring Beep. I opened up the case to get some more photos and to look for clues.

The problems started when I unplugged a flexi-pcb type ribbon connector or more correctly plugged it back in. There was a neasty cracking sound and more no more beeping.

I have clearly cracked the ribbon.

More bad-ish things in that my Mac Mini has decided that it doesn’t want to run in this hot weather and so I can’t get to my photos etc.

More of my computing time hace been spent getting another machine up and running. Ironic really that I am surrounded by machines but most are too retro to use for email, web editing, photos etc. (Yes I know you can connect a Spectrum to the ‘net but come on… Seriously)

I now have an old Dell rackmount server as my PC running Ubuntu 🙂

A bit of good news came in the form of an email from another Liberator owner, Peter, from Wales who has leapfrogged my efforts with some wonderful information an old school cunning. He is really on the ball with this and leaving me in the dust but a very welcome contact.

When I can I will sort out another cable and be back on the trail.

July 16 2013. More batteries.

I’ve found a set of batteries 🙂 Woo Hoo.

I’ve soldered them onto the PCB and fitted them into the batter pack. I’m back with the Beep now.

More investigation to follow.

July 10. 2013. Batteries.

The Liberator has a removable battery pack that was filled with four very fluffy batteries. I disposed of these very quickly, cleaned the board and tried to see what was what. An interesting feature is that the battery pack contains its own charging circuit so the 9V DC power supply plugs into the battery. I haven;t come across any other portable computer that does it this was. All of the others have the DC socket as part of the laptop. That’s curious.

These days you can’t get NiCd batteries any more and so I’ve been thinking of what to do.

I’ve taken the PCB layout of the charger board that’s in the battery pack and drawn what I think is the circuit diagram.

The key component here is the LM317, a voltage/current regulator, which appears to be rigged to limit current. A freind at work suggested that if it’s in that state I could replace the NiCds with NiMHis. Their life wouldn’t be great but they would work.